4 Weeks Pregnant: Baby is as big as a poppy seed!

4 Weeks Pregnant: Baby is as big as a poppy seed!

Week 4 at a glance

If you’re asking the question, is 4 weeks pregnant really 2 weeks?, don’t worry.

You haven’t lost your ability to do simple math.

You’re right! In the world of pregnancy, 4 = 2.

Your last period is the point at which doctors start the timer, simply because this is easier to track than ovulation and conception.

You’re not in fact pregnant-pregnant until about 3 weeks later.

So, while it may sound like you’re further into this journey than you are, 4 weeks pregnant is not too far from the starting line.

In this article: 📝

  • Week 4 at a glance
  • Baby development at 4 weeks
  • Pregnancy symptoms at 4 weeks
  • Pregnancy tips at 4 weeks

Baby development at 4 weeks

The Great Burrow

By now, your baby/blastocyst has burrowed into the lining of your uterus ‒ and no doubt into every waking thought you have.

The Great Divide

Once your blastocyst is firmly settled in its new home, it splits into two.

The inner cells begin to form into the embryo (and in turn into your baby’s various parts) and the outer cells into the nourishing yolk sac.


As the embryo develops, it forms into 2 and then 3 different layers.

The layer in the center is now at work to form the respiratory and digestive systems.

Surrounding this, the middle layer is forming into the heart, blood, and bones.

The outer layer is what will become the brain and nervous system.

Essentially, what was once a simple zygote is starting the job of becoming a person.

Yolk sac

This is your baby’s first diner.

In a few weeks, this simple yolk sac will transform into the placenta.

The job of the placenta is to connect your forming baby to the support and nourishment that your body offers it.

How big is a 3-week fetus?

At this point, your baby-to-be is about 0.2mm.

That’s the size of the circumference of a piece of pencil lead!

While an ultrasound at 4 weeks pregnant is not typical – often, parents-to-be wait until about 6 weeks – you could take a trip to the doctor at this point to get a glimpse inside.

So how are you going to be feeling through all of this?

Pregnancy symptoms at 4 weeks

The first most noteworthy symptom is that your period doesn’t show up when it should (there can of course be other reasons for its absence but this is most certainly one of the possibilities).

So what is actually happening when your period decides to ditch you when it gets word of conception?

Well, your body is making the pregnancy hormone hCG.

In one of the many examples of our bodies’ incredible internal communication system, the hormone is signaling to your ovaries that they don’t need to release an egg each month.

It also ups the production of estrogen and progesterone.

Remembering that everybody (every body) is different, some possible symptoms you may experience are:

  • Bleeding in early pregnancy 4 weeks. You may experience some spotting at 4 weeks pregnant. This is likely the result of the blastocyst implanting itself in the lining of your uterus.
  • Hormone frenzy. All of these hormones can leave you feeling everything from hot to moody to bloated to having a racing heart. Many of these feelings can be indistinguishable from PMS.
  • Morning sickness. While 4 weeks pregnant is a bit early for morning sickness, which typically appears closer to 6 weeks, it is possible to have nausea and vomiting at this point in your pregnancy.

Pregnancy tips at 4 weeks

We know it’s early, but it’s never too soon to start planning for your pregnancy journey.

Here are a few things to consider adding to your to-do list:

  • Schedule a pregnancy confirmation appointment ‒ your healthcare provider can give you the best advice from here on.
  • Get a cute pregnancy journal ‒ documenting your pregnancy journey is a great way to look back on this special time in your life. Get a cute pregnancy journal and fill it with memories, milestones, and baby bump photos.
  • It’s totally up to you when to share the big news, but having some support from a partner or close family member can make all the difference.
  • Start taking a prenatal vitamin if you’re not already ‒ prenatal vitamins are specially formulated to provide you and your growing baby with the nutrients you need. Talk to your healthcare provider about which one is right for you.
  • Time to think about those lifestyle changes, mama! Whether it’s tweaking your diet or finding new ways to relax, let’s plan ahead and set you up for success.

Look, you might be visiting all the points of the happiness spectrum ‒ and that’s totally normal.

Of course, this feels huge!

You’re growing a person! It is also the journey of a lifetime that may feel at times magical, at times stress-inducing, and at times, like pure bliss.

Know that you’re allowed to feel all of it!

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